Finally, for today's extra credit: the history of the doggie bag. Apparently ancient Romans brought napkins to dinner in order to wrap leftovers, but the purpose-built doggie bag was invented in the early 1940s, during World War II food shortages. Etiquette experts such as Emily Post were horrified when people started using the bags for leftovers they intended to eat themselves, but today, in an era of portion supersizing and rampant food waste, it's the smart thing to do.